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Old 13th April 2012, 11:17 AM   #1
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Default SJ5492F transistor replacement needed!

Hi folks, come across an interesting part that I can find very little info about, a Motorola SJ5492F transistor. I am repairing an old amp that has one of these per side, along with its NPN counterpart. Has anyone ever come across these or have any info on them?

From measuring the good one in the other channel, I can say that it is a BJT and is PNP, in a TO-3 case. It's driver transistor is a MPS-U56 and info is readily available for these, but I could find nothing about the SJ5492F. The closest I came to finding anything was a thread in some foreign language audio website where the OP had pretty much the same problem as I.
I can get a replacement driver transistor (it was shorted as well as the mentioned power transistor) but it looks as if I may need to substitute a pair to replace an unknown type.

What are the best ways to do this? I will remove all shorted components and then power the amp up to measure its rail voltage, but I'm not too sure what else to take into consideration. It is an old amp made in NZ about 30 years ago so no info or schematics available. As always, any helpful info is greatly appreciated and all suggestions are welcome.
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Old 14th April 2012, 02:31 AM   #2
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If it's 30 years old I would use the MJ15004.
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Old 14th April 2012, 02:47 AM   #3
srh is offline srh  New Zealand
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Hi flyingtele, they are 80V, 10A rated devices. I have some pulls available if you are interested.
Regards, Steve.
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Old 14th April 2012, 08:28 AM   #4
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So it's a house-numbered 2N3792 then.
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Old 14th April 2012, 10:11 AM   #5
srh is offline srh  New Zealand
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djk, no,it's from the numbering scheme Motorola used in the 70's. It has a pnp complement, SJ5493F. Motorola describes them as a low cost comp. pair suitable for amp, switches and regulators. Info comes from the 1976 selector guide.Several local manufacturers of hifi and instrument amps used them, mainly in quasi-comp circuits.
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Steve.
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Old 14th April 2012, 12:44 PM   #6
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Are you sure, I always thought SJ numbers were always 'specials', and Motorola would not give out any info on them?

At best they were selected (or screened) versions of standard parts.

"It has a pnp complement, SJ5493F."

Now I'm confused, flyingtele thinks the SJ5492F a PNP.

The complement to the PNP 2N3792 would be the NPN 2N3716.

http://www.datasheetcatalog.org/data...ola/2N3716.pdf
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Old 14th April 2012, 10:31 PM   #7
srh is offline srh  New Zealand
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Hi djk, I'm as sure as the Motorola selector guide 1976 edition allows me to be! I put a SJ5492F on my analyser, it's a NPN. A 2N3716 would be a good substitute.
Regards,
Steve.
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Old 15th April 2012, 10:48 AM   #8
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Hi Flyingtele i worked for Rait Electronics in the late 70's and both the 30-30 and 60-60 used these transistors along with a few other manufacturers of that time like neeco and sonophone.
I have repaired many Rait amps over the years upgrading them with MJ15003/4
and these work well as substitutes for the SJ's.
Regards Peter.
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Old 15th April 2012, 01:56 PM   #9
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I just dug out my Motorola Master Selection Guide and blew the dust off of it. Pages 155 thru 157 cover the TO-3 power transistors. There is no mention nor anything in print on the SJ transistors. The "SJ's" are special
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